1. Field of the Invention
The present invention relates to a beam-forming apparatus and related method, more particularly, to a beam-forming apparatus applied in a multiple input multiple output system.
2. Description of the Prior Art
A primary concept of a multiple-input multiple-output (MIMO) system is having a plurality of antennas installed on a transmission end and a receiving end for receiving and transmitting data through a channel between the plurality of antennas. For example, please refer to FIG. 1. FIG. 1 illustrates a diagram of a conventional MIMO system 10. The MIMO system 10 includes a transmission end 20 and a receiving end 30, three antennas 22, 24, 26 are installed on the transmission end 20, and two antennas 32, 34 are also installed on the receiving end 30, therefore data transmitted by the transmission end 20 to the receiving end 30 passes through 3*2 channels 42, 44, 46, 48, 52, 54. If the transmission end 20 transmits two data streams D1, D2 simultaneously to the receiving end 30, then the transmission end 20 will multiply the data streams D1, D2 by a gain vector and form three transmitted signals S1, S2, S3 to be transmitted respectively through the antennas 22, 24, 26. A method of generating the transmitted signal S1, S2, S3 can be represented by the following formula:S1=D1*V1,1+D2*V1,2  Formula (1)S2=D1*V2,1+D2*V2,2  Formula (2)S3=D1*V3,1+D2*V3,2  Formula (3)
Regarding the formulas above, the three vectors [V1,1, V2,1, V3,1]T are utilized for determining the portion of the transmitted signal S1, S2, S3 in the data stream D1, therefore the three vectors [V1,1, V2,1, V3,1]T can be viewed as a transmitting vector of the data stream D1; similarly, the three vectors [V1,2, V2,2, V3,2]T are utilized for determining the portion of the transmitted signal S1, S2, S3 in the data stream D2, therefore the three vectors [V1,2, V2,2, V3,2]T can be viewed as a transmitting vector of the data stream D2.
To separate the data stream D1 from the data stream D2 after the wireless transmission, a conventional technology utilizes a singular value decomposition (SVD) method to determine the transmitting vectors [V1,1, V2,1, V3,1]T, [V1,2, V2,2, V3,2]T, such that the data stream D1 and the data stream D2 are orthogonal to each other. However, the SVD method of generating the transmitting vectors [V1,1, V2,1, V3,1]T, [V1,2, V2,2, V3,2]T requires a high volume of floating point calculation which guarantees a high volume calculation consumption. Furthermore, in utilizing the SVD method, it is unavoidable that problems will arise. The problems include the power distribution between the antennas being unequal and thereby the high requirement for PA (power amplifier) linearity accompanied with the increase of cost is necessary.